This invention is related to the field of telecommunications, particularly to radiotelephony, and more particularly to using radiotelephony technology for tracking and recovering stolen vehicles.
There are several obstacles to minimize damages caused by vehicle theft, and among them is the quick recovery. The recovery of a stolen vehicle hinges on early notification about the theft and quick localization of the vehicle. Currently, many theft prevention and recovery systems are available for consumers, but most of them either do not address the problems above simultaneously or are expensive for most car owners.
A typical automobile theft prevention device includes sensors disposed around a vehicle that detect designated events. These designated events typically include unauthorized entry, excessive movement of the vehicle, unauthorized attempts to start the vehicle, and unauthorized attempts to remove one or more components located within the vehicle. Unauthorized entry events typically include the opening of the hood, the opening of the trunk, and the opening of the vehicle""s doors. One or more motion sensor is typically used to determine whether there is sufficient movement of the vehicle so as to indicate a possible theft. This provides a triggering of the alarm when there is an attempt to tow the vehicle or place the vehicle on a car carrier. Unauthorized attempts to start the car also indicate possible vehicle theft. In addition, attempts to remove a component such as a stereo or a CD player also may indicate a possible theft.
Upon occurrence of an unauthorized event, the alarm triggers as an attempt to scare the thief off. However, the owner is not notified, unless the owner is nearby and able to hear the alarm. When the owner realizes the vehicle is stolen, often the vehicle is miles away and the owner is powerless to do anything.
Some inventions have been made to allow vehicle owners to remotely shut down vehicles after they have been stolen. A system that provides this capability through wireless transmission technology is described in U.S. Pat. No. 5,276,728, Remotely Activated Automobile Disabling System, to Pagiliaroli (Jan. 4, 1994), which is hereto incorporated by reference. However, Pagiliaroli""s system does not provide any indication about the location of a stolen vehicle after it has been disabled.
Once the vehicle is stolen, the recovery is not easy, unless it can be located rapidly. There are few devices that aid vehicle recovery, and a well known one is LOJACK(trademark). LOJACK(trademark) is a relative expensive system that provides after-the-fact retrieval system. The system requires local law enforcement agencies to be equipped with a special tracking system besides an individual device to be installed on vehicles. The device is always in a receiving mode and it is triggered by a radio signal. After the system is triggered, it emits a radio signal, which has a ground range of only a few miles, that allows law enforcement personnel to track its location and ultimately to locate the vehicle.
Another well-known system is OnStar(trademark), which uses Global Positioning System for locating a vehicle and wireless telephone network for communicating with its occupants. Global Positioning System (GPS) satellite technology works by measuring how long it takes a radio signal from a satellite to reach a vehicle, and then calculating distance using that time. Radio waves travel at the speed of light, which is 186,000 miles per second. GPS satellites are launched into very precise orbits and are constantly monitored by the Department of Defense to measure their altitude, position, and speed. Both the satellite and the GPS receiver in the vehicle are generating the same signal, called a pseudo-random code. OnStar(trademark) can calculate the time by comparing how late the satellite""s pseudo-random code is compared to the receiver""s. That time difference is then multiplied by 186,000 miles per second, giving a vehicle""s distance from one satellite. To get the most accurate vehicle location, OnStar(trademark) uses the measurement from four satellites.
The aforementioned systems either require special support from local law enforcement authorities to locate the stolen vehicles or require the vehicles to be equipped with expensive GPS tracking equipment for determining their locations.
Briefly described, the present invention is a system and method that employ wireless telecommunication technology and location information of a wireless device to locate and recover stolen vehicles or valuable objects. According to the present invention, a vehicle is equipped with an anti-theft device capable of making wireless calls to a monitoring center. The monitoring center is capable of locating the vehicle through a wireless network configured with multiple radio-direction-finding (RDF) devices in multiple wireless transmission antenna sites, one RDF device per each transmission antenna site. The RDF devices are connected to a location processor, where the position calculations are performed. The location processor is in communication with a Mobile Switching Center (MSC) that is handling the communication with the radiotelephone. The monitoring center is also capable of sending special commands to the anti-theft device for shutting down or otherwise immobilizing the vehicle.
A vehicle owner may purchase a theft detection device and corresponding theft monitoring service from a theft monitoring service provider. The theft detection device can be any commercially available theft detection device capable of connecting to a theft monitoring center through a wireless telephone network. The vehicle owner can predetermine actions to be taken upon occurrence of certain events and the prescribed actions are stored in a database at the theft monitoring center.
The theft detection device may be programmed to place a call to the theft monitoring center upon occurrence of some specified events. A specified event may be the pressing of the panic button, activation of an air bag, unauthorized use of the vehicle, etc. The theft detection device serves as a tracking device while it is in communication with the monitoring center.
The theft monitoring center may also initiate a call to a theft detection device installed on a vehicle after receiving a call from its owner. An owner, upon realizing his automobile has been stolen, can place a call to a theft monitoring center to report the stolen vehicle. The theft monitoring center will then place a call to the stolen vehicle and at the same time request that the position of the stolen vehicle be determined.
Typically, the call and the request are routed through a Public Switched Telephone Network (PSTN) to a Mobile Switching Center (MSC), and the MSC routes the call to the theft detection device installed on the stolen vehicle. After the call is answered by the theft detection device and the connection established between the theft detection device and a base station (BS) of a wireless telephone network, the MSC forwards the location request to a location processor along with radio signal information.
The location processor is a processor that controls a plurality of RDF devices and determines the location of a radio signal""s source. The location processor obtains the radio signal""s information (frequency, time slot, channel, etc.) from the MSC and sends this information to the RDF devices. Each RDF device attempts to determine the angle of arrival of radio signals relative to the position of the RDF device. Preferably, two or more RDF devices can determine the angles of arrival. This information is sent to the location processor.
The location processor uses the angle of arrival information and the information on the location of RDF devices to calculate the geographical coordinates of the source of the radio signal. The geographical coordinates calculated are then used to determine the street address of the caller.
If more than two RDF devices detect the radio signal, the location processor will determine several pairs of geographical coordinates by pairing RDF devices differently. Using these pairs of geographical coordinates, the location processor will determine the location of the source of the radio signal.
If only one RDF device detects the radio signal, then the angle of arrival is provided to the MSC and the location processor does not calculate the location of the radio signal""s source.
After the street address is determined, the location processor sends it to the theft monitoring center. The theft monitoring center can then take appropriate action such as requesting police assistance, shutting down the vehicle, etc.